Changing Partition Map of a Drive

Discussion in 'OS X Yosemite (10.10)' started by haravikk, Jan 15, 2015.

  1. haravikk macrumors 65816

    May 1, 2005
    Okay, so I've upgraded an older system to Yosemite for a friend, and they'd like to have their Time Machine volume encrypted using Filevault/Core Storage, however it's currently using an Apple Partition Map, meaning it needs to be erased in order to do this through Time Machine itself.

    Now, I know that changing a partition map isn't really an option, so I obviously need to backup the volume, erase it and restore it as GPT.

    I'm just hoping to find out the exact steps for doing this as easily as possible.

    I'm sure I've tried something similar in the past and had tremendous trouble due to a backup image being very slightly larger than the newly formatted partition I wanted to restore it onto (by only a few bytes due to partitioning overhead), so I'd just like to confirm the easiest way to do this without these kinds of problems :)
  2. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    You will need a target volume that is at least slightly larger than the source.

    Open Disk Utility and go to the restore tab and drag the source volume into the source tab and the destination volume into the destination tab then click restore. That will clone the source to the destination.

    Now go to the partition tab and set it to 1 partition for the disk and in options set it to GUID then apply.

    Now go to the erase tab and reformat the Mac OS Extended (Journaled, Encrypted) and follow the prompts to set a password.

    Now use Disk Util to resize the partition where you moved the data so it is slightly smaller than your new encrypted volume. The use the restore process in reverse to clone the data back to the encrypted volume.
  3. grahamperrin macrumors 601


    Jun 8, 2007

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